1. Field
The presently disclosed subject matter relates to an illumination device in which a plurality of radiation fins are disposed radially for dissipating heat generated by a light emitting element. In particular, the disclosed subject matter relates to an illumination device which is capable of radially radiating light generated from a light emitting element while the efficiency of dissipating heat from the light emitting element can be improved and in which the utilization efficiency of the light from the light emitting element can be improved.
2. Description of the Related Art
An illumination device has conventionally been known in which a plurality of fins for dissipating heat (radiation fins) are disposed radially for dissipating heat generated by a light emitting element (e.g., a light emitting element chip). An example of an illumination device of this type includes an illumination device described in Japanese Patent Laid-Open Publication No. 2005-93097.
The illumination device described in this publication is configured to include a plate-like base member, insulative heat sinks disposed on the plate-like base member, and light emitting element chips disposed on the respective insulative heat sinks. Furthermore, the illumination device is configured to include a cylindrical supporting body attached to the lower side (the rear face side) of the base member, and a plurality of rectangular plate-like fins for dissipating heat (radiation fins), attached to the outer peripheral surface of the cylindrical supporting body.
In this illumination device, the heat generated by the light emitting element chips is dissipated from the radiation fins through the insulative heat sinks, the base member, and the supporting body.
In the illumination device, the insulative heat sinks are disposed rearward in the central axis direction of the illumination device with respect to the light emitting element chips. The base member is disposed rearward with respect to the insulative heat sinks in the central axis direction. In addition, the supporting body and the radiation fins are disposed rearward with respect to the base member in the central axis direction.
Therefore, the radiation fins are disposed at positions relatively distanced from the light emitting element chips in the central axis direction of the illumination device. Hence, the heat conduction path from the light emitting element chips to the radiation fins is long. Therefore, the heat dissipation efficiency of the radiation fins is low.
Meanwhile, in order to reduce the length of the heat conduction path from the light emitting element chips to the radiation fins, it is conceivable that the supporting body and the radiation fins are disposed radially outside of the light emitting portion having the light emitting element chips. In other words, the supporting body and the radiation fins can be disposed at positions which are not rearward with respect to the light emitting element chips in the central axis direction of the illumination device. However, in such a case, the light radially emitted from the light emitting element chips may be blocked by both the supporting body and the radiation fins which are both radially arranged. Therefore, the light from the light emitting element chips cannot be efficiently radiated in the radial direction of the illumination device.